Many techniques are available for increasing the physical (PHY) layer throughput of wireless networks. One technique is to increase the bandwidth of a channel, for example from 20 Mhz to 40 Mhz, etc. However, in some frequency bands, the ability of a secondary user to use a channel may be constrained by whether the secondary user can detect whether a primary user (e.g., radar) is present. If the primary user is present, then the secondary user cannot use the channel.